1. Properties of Liquids and Solids

2. Intermolecular Forces
Intermolecular Forces: weaker interactions that occur between molecules. These are collectively known as Van der Waals forces.
Intramolecular Forces: Do not confuse Inter with Intra! Intramolecular forces are how we describe bonding between atoms.

3. Intermolecular Forces

4. Types of IMF
London Dispersion Forces
View animation online.

5. Types of IMF
Dipole-Dipole Forces + -
View animation online.

6. Types of IMF
Hydrogen Bonding

7. Liquids vs. Solids SOLIDS LIQUIDS IMF Strength Very strong
Fluid
Density
Compressible
Diffusion
SOLIDS
Very strong N
high
extremely slow
LIQUIDS
Stronger than in gases Y
high N
slower than in gases

8. Liquid Properties Surface Tension
attractive force between particles in a liquid that minimizes surface area

9. Liquid Properties Capillary Action
attractive force between the surface of a liquid and the surface of a solid
water
mercury

10. Liquid Properties
Viscosity: Resistance to flow (molecules with large intermolecular forces).

11. Types of Solids Crystalline - repeating geometric pattern
covalent network
metallic
ionic
covalent molecular
Amorphous - no geometric pattern
decreasing
m.p.

12. Types of Solids
Ionic
(NaCl)
Metallic

13. Types of Solids Covalent Molecular Covalent Network Amorphous (H2O)
(SiO2 - quartz)
Amorphous
(SiO2 - glass)

14. Types of Solids

15. Types of Solids: Metals
The electron sea model for metals postulates a regular array of cations in a "sea" of valence electrons. (a) Representation of an alkali metal (Group 1A) with one valence electron. (b) Representation of an alkaline earth metal (Group 2A) with two valence electrons.

16. Types of Solids: Metals
Alloy: A substance that contains a mixture of elements and has metallic properties
Substitutional Alloy (a): some of the host metal atoms are replaced with atoms similar size metal atom
Interstial Alloy (b): some of holes between the metal atoms are filled with smaller atoms

17. Phase Changes

18. Phase Changes Evaporation
molecules at the surface gain enough energy to overcome IMF
Volatility
measure of evaporation rate
depends on temp & IMF

19. Phase Changes Equilibrium
trapped molecules reach a balance between evaporation & condensation

20. Phase Changes temp v.p. IMF v.p. Vapor Pressure
pressure of vapor above a liquid at equilibrium
v.p.
depends on temp & IMF
directly related to volatility
temp
temp
v.p.
IMF
v.p.

21. Phase Changes Patm b.p. IMF b.p. Boiling Point
temp at which v.p. of liquid equals external pressure
depends on Patm & IMF
Normal B.P. - b.p. at 1 atm
Patm
b.p.
IMF
b.p.

22. Phase Changes IMF m.p. Melting Point equal to freezing point
Which has a higher m.p.?
polar or nonpolar?
covalent or ionic?
polar
ionic

23. Phase Changes Sublimation solid  gas
v.p. of solid equals external pressure
EX: dry ice, mothballs, solid air fresheners

24. Heating and Cooling curve

25. Heating Curves Temperature Change change in KE (molecular motion)
depends on heat capacity
Heat Capacity
energy required to raise the temp of 1 gram of a substance by 1°C -

26. Heating Curves Phase Change change in PE (molecular arrangement)
temp remains constant
Heat of Fusion (Hfus)
energy required to melt 1 gram of a substance at its m.p.

27. Heating Curves Heat of Vaporization (Hvap)
energy required to boil 1 gram of a substance at its b.p.
usually larger than Hfus…why?
EX: sweating, steam burns, the drinking bird

28. Phase Diagrams
We know that different compounds can have different phases.
These phases depend on the temperature and pressure of the substance.
Temperature
Pressure
We can then use that information to create a diagram of the different phases called a PHASE DIAGRAM.

29. Looking at Phase Diagrams
The boundaries between phases occur at phase changes (ie. melting, freezing, vaporizing, etc.) S L G
Temperature
Pressure
A - melting, freezing A B
B - vaporization, condensation
C - sublimation, deposition C

30. Looking at Phase Diagrams
The triple point is where the boundaries converge at one point and all three phases are present at the same time. S L G
Temperature
Pressure
Triple Point

31. Looking at Phase Diagrams
The critical point is the point at which the distinction between the liquid phase and gas phase ceases to exist. S L G
Temperature
Pressure
Critical Point

32. Determining the Melting Point
Find the current pressure
Draw a line across the diagram
At the boundary between the solid and liquid phase, draw a line down to the temperature
Determine the temperature S L G
Temperature
Pressure
1 atm

33. Phase Change of Water

34. Phase Diagrams
Each substance or compound has different melting/freezing points, boiling/condensing points, and sublimation/deposition points.
Therefore, each substance or compound has a different phase diagram.
Carbon